Lumber bin sorter with vertically-positionable and tiltable bin floors

ABSTRACT

A lumber bin sorter, of the type having a multiplicity of bins to which graded green lumber is carried by an overhead conveyor and ejected into designated bin locations, wherein each of the bins is provided with a vertically positionable floor member which is raised to the topmost position when the bin is empty and then, as the bin fills up with lumber, the floor indexes successively downward until it reaches the lowest point when the bin is full. The floor, which is guided in its travel by a cam follower mechanism, thereafter tilts downward to provide an opening in the bottom of the bin for dumping its contents onto a conveyor chain traveling underneath. Appropriate sensors, in the form of limit switches and photocells, are provided to generate control signals indicating the arrival of the bin floor at the respective uppermost and lowermost pints of travel and for causing the floor to index downward in response to the progressive filling of the bin with lumber.

United States Patent Turner et a].

Apr. 4, 1972 [54] LUMBER BIN SORTER WITH VERTICALLY-POSITIONABLE ANDTILTABLE BIN FLOORS [72] Inventors: Donald B. Turner; Albert II. Barnes,both of Portland, Oreg.

[73] Assignee: Moore Dry Kiln Company of Oregon, Portland, Oreg.

[22] Filed: June 12, 1970 [21] Appl. No.: 45,819

52] us. Cl. ..209/74, 214/6 H [51] Int. Cl ..B07c 3/08 [58] Field ofSearch ..209/74, 73, 125; 214/6 DK,

[56] References Cited UNITED STATES PATENTS 3,085,686 4/1963 Hanbury..'..209/74 UX 3,533,517 10/1970 Heide Primary Examiner-Allen N. KnowlesAttorney-Daniel P. Chernoif [57] ABSTRACT A lumber bin sorter, of thetype having a multiplicity of bins to which graded green lumber iscarried by an overhead conveyor and ejected into designated binlocations, wherein each of the bins is provided with a verticallypositionable floor member which is raised to the topmost position whenthe bin is empty and then, as the bin fills up with lumber, the floorindexes successively downward until it reaches the lowest point when thebin is full. The floor, which is guided in its travel by a cam followermechanism, thereafter tilts downward to provide an opening in the bottomof the bin for dumping its contents onto a conveyor chain travelingunderneath. Appropriate sensors, in the form of limit switches andphotocells, are provided to generate control signals indicating thearrival of the bin floor at the respective uppermost and lowermost pintsof travel and for causing the floor to index downward in response to theprogressive filling of the bin with lumber.

3 Claims, 4 Drawing Figures Patented April 4, 1972 3 Sheets-Sheet F)LUMBER BIN SORTER WITI-I VERTICALLY- POSITIONABLE AND TILTABLE BINFLOORS BACKGROUND OF THE INVENTION This invention relates toimprovements in a bin sorter for green lumber of the type whereinsimilar graded lumber is conveyed and dropped into a designated one of amultiplicity of bin storage locations. More specifically, the inventionrelates to a bin sorter of the type described wherein the individualbins are provided with a vertically positionable floor or support memberwhich is indexable in increments between an uppermost position, usedwhen the bin is empty, and a lowermost position at which the floorarrives when the bin is full. The apparatus also includes means to tiltthe floor for emptying the contents of the bin through its bottom onto aconveyor for removal to another location and associated sensors forgenerating actuating signals for controlling the travel of the binfloor.

In lumber bin sorters, of the type known to the art and shown forexample in Boyle US. Pat. No. 3,254,764 and Rambo US. Pat. Nos.2,902,150 and 2,998,133, assorted green lumber is conveyed on ahorizontal path by an overhead conveyor and ejected, at the appropriatemoment, to fall downward into a predetermined one of a plurality ofreceiving bins or bin locations assigned to a particular grade anddimension of lumber. Since the variations of lumber width, length,thickness, moisture content, species, grade, and the combinationsthereof, are considerable, a typical such sorter would possess a largemultiplicity of bin locations, perhaps 20 to 50.

In conventional bin sorters of the type described, the first sticks oflumber dropped into an empty bin location typically fall through adistance of 7 to 8 feet onto a flat, hard floor of a trolley or buggycar, and consequently these initial sticks frequently are damaged anddegraded. Furthermore, because of the lengthy fall distance as the binis initially filled, and the inevitable asynchronous operation of theejection means which causes one end of the lumber to be dropped ahead ofthe other from the conveyor into the bin, the lumber sticks tend tojackstraw or randomly align, so that the lumber pile does not build upuniformly in the bin. In an effort to overcome this last-mentionedproblem, prior art drop sorters have heretofore commonly been providedwith two spaced sets of ejection means for each bin location so that theboards falling into a designated bin location would alternately bedropped first near one wall and then near the other wall of the bin.However, this expedient, while alleviating somewhat the problem ofnon-uniform buildup, does nothing to prevent the problem of lumberdegrade on the initial boards falling into the bin, and the addition ofan extra set of ejection elements for each bin location increases thecost and complexity of the sorter apparatus and its associated controls.Furthermore, in conventional lumber bin sorters emptying of the bincontents and their removal to another work station is a time-consumingprocess involving several workers to minimize downtime and expedite theoperation, since it is required that the filled buggy originallypositioned in the bin location be wheeled out, moved over to the nextstation, and its contents emptied, a second buggy wheeled in underneaththe sorter to replace it, and a third buggy made ready for standby.

Accordingly, a real need exists in the industry for a lumber drop sorterapparatus of economical and rugged construction which will overcome theaforementioned disadvantages of prior art devices.

SUMMARY OF THE PRESENT INVENTION The present invention is directed to abin sorter apparatus of the general type described in which each of theholding bins is provided with a vertically positionable floor supportmember which can be raised up to the top of the bin when it is empty andthereafter successively indexed downward as the bin fills up withlumber. In the uppermost position the bin floor is only a few feet atmost from the conveyor so that the ejected lumber need only fall arelatively short distance before coming to rest on the bin floor, thusvirtually obviating the possibility of damage or degrade of the initialboards. Also, as the dropped boards strike against the bin structure andagainst each other far more gently and fall over a substantially lesserdistance, they tend to line up more uniformly and in proper orientation,resulting in a more compacted loading of the bin. Consequently, theprovision of a vertically positionable floor in the bin frequentlyallows the second set of ejection elements to be eliminated at each binlocation, thereby effecting considerable savings and also permitting thebins themselves to be made narrower, thus reducing the overall size ofthe sorter apparatus with attendant further savings in material andspace.

When the bin location is completely filled with the bin floor loweredaccordingly, the floor can then be tilted downward to form an opening atthe bottom permitting the bin contents to be quickly emptied onto aconveyor chain passing underneath for removal and direct infeed to astacker or other work station remote from the sorter apparatus.

The vertical travel and tilting of the bin floor is guided by a camfollower mechanism, and the travel is controlled by sensors forgenerating respective control signals upon the floor reaching itsuppermost position when empty, as the bin container then progressivelyfills up with lumber, and finally as it reaches the lowermost positionprior to dumping. The cam guide is provided with a fishtail curve on thedown-travel end which permits the bin floor, after lowering to the fullyloaded index position of the storage bin, to thereafter follow a curvedpath and cause the floor to tilt in a downward vertical arc to gentlydump the contents onto the conveyor underneath, The utilization of aconveyor to carry off the bin contents, rather than a buggy or trolleycar as conventional, enables the individual bins of the sorter apparatusto be emptied and quickly replaced into service ready for refilling.

It is therefore a principal objective of the present invention toprovide a new and improved bin sorter for lumber and like material whichis of more economical design, minimizes the possibility of damage ordegrade of the material in the sorting process, builds up a morecompact, uniform and aligned pile in the bin, and provides means formore rapidly emptying the filled bin, removing its contents to asubsequent work station and replacing the emptied bin back intooperation with considerably less manpower required than with prior artdrop sorter systems.

It is a principal feature of the present invention to provide a binsorter of the type described wherein each of the bins is provided with avertically positionable and tiltable support floor which may be raisedto the topmost position when the bin is emptied and then, as the binfills up with lumber, the floor indexed successively downward until itreaches the lowest point when the bin is full, and thereafter the floormay be tilted downward to provide an opening in the bottom of the binfor dumping its contents onto a conveyor traveling underneath for theirremoval to a remote work station.

It is a further feature of the present invention to provide sensors in abin sorter of the type described to generate actuating signals forcontrolling the travel of the bin floor and for indicating the fillcondition of the bin.

The foregoing and other objectives, features and advantages of thepresent invention will be more readily understood upon consideration ofthe following detailed description of the invention, taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front sectional view of anillustrative embodiment of the lumber bin sorter apparatus of thepresent invention, showing several individual holding bins at differentstages of operation.

FIG. 2 is a top plan view of an individual holding bin, exemplary of themultiplicity of such bins provided in the sorter apparatus of thepresent invention, with the overhead conveyor mechanism removed forpurposes of clarity.

FIG. 3 is an end sectional view of an individual holding bin, takenalong the line 3-3 in FIG. 2.

FIG. 4 is an enlarged perspective view, partially broken away and withcertain repetitive chain and sprocket elements represented in phantomlines, showing the drive mechanism for the movable bin floor employed inthe sorter apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I initially,the bin sorter, designated generally as 10, comprises an overheadconveyor mechanism 14 for delivering individual pieces of graded lumberto a point above a designated bin location and thereafter ejecting thelumber piece into its assigned bin 20. In the fragmentary drawing ofFIG. I, only five bin locations 20a...20e are shown, but this isintended to be representative of a large multiplicity of such binlocations in a typical sorter embodiment. Upon emptying of a particularbin, for example 200, the contents are dumped onto a conveyor 80traveling underneath and thereafter carried to a remote work station forstacking or other operation.

Considering now more particularly the major components of the bin sortersystem, the overhead conveyor 14 is conventional and formed of aplurality of endless conveyor chains from which are suspended sets ofspaced carrier elements or J- bars 15 supporting individual boards 16aligned transversely to the direction of travel of the conveyor (rightto left in FIG. I). When a given board 16 is directly above itsdesignated bin location, pivotal diverter elements 18 are caused torotate down so as to be interposed in the path of the board travel (asshown at bin location 20d) and cause the board to slide off itsassociated carrier bar 16 as the conveyor continues its travel, thusejecting the board into the assigned bin location. The operation of therespective diverter elements 18 at the appropriate moment to cause theboards to fall into their designated bin locations, so that anindividual bin location contains only boards of similar type, iscontrolled by visual categorization by the operator as to species andgrade and by appropriate sensors for automatically determining boarddimensions and moisture content located at the infeed of the conveyor,together with associated memory and logic circuitry. Means for effectingthe automatic operation of the diverter elements so as to eject boardsinto their designated bin locations are well known to the art, as shown,for example, in Davies US. Pat. No. 3,495,707, and form no part of thepresent invention. On occasion it will be desirable in certainembodiments of the invention to provide two sets of diverter elements 18at each bin location, one near the front wall of the bin and the othertoward the rear, and their actuation alternated so that successiveboards are ejected from the conveyor first near one wall then near theother wall of the bin to improve the uniform buildup of the pile.

Referring now to FIGSv 2 and 3 in addition to FIG. 1, an individual binlocation 20 is in the form ofa stall having front and rear walls 22, 24mounted on a skeletal frame 26 and carried on support stanchions 28. Thebottom edge of each wall 22, 24 is elevated above ground to provideadequate clearance for a loaded chain conveyor 80 passing underneath.

A movable floor member 30 is provided in each bin stall, bridging thespace between the two vertical walls, to catch and support the boardsdropping into the bin. The floor member is formed of a plurality ofsupport arms 32 projecting out from and axially spaced along a commonhorizontal shaft 34 aligned parallel to the bin walls and supported by achain mechanism 42 hereinafter described. The floor support arms 30which project forwardly of the front wall 22 of the bin are preferablyeach provided with a rearwardly extending shield portion 33 which, inthe horizontal position of the support arm, is angled upwardly towardthe near wall so as to guide lumber toward the center and prevent boardsfrom jamming between the shaft and the wall. The arms are spacedsufficiently close together, typically on 4-foot centers, so thatadequate support is provided for the lumber carried thereon withoutundue concentration of stress.

Attached to either end of the tubular shaft 34 is a pair of upper andlower radial flanges 38, 39 each carrying an associated roller camfollower 38a, 390 which ride on respective track surfaces 40a and 40b ofcam guide 40 carried on the wall stanchion 28. The upper radial flange38 on each end of the shaft 34 is connected to the supporting cableassembly 42 which raises and lowers the floor member 30 as the camfollowers 38a, 39a ride on their respective tracks of the cam guide 40.As the supporting cable is slackcned, cam followers 38a, 39a follow avertical path along their respective tracks 40a, 4012 until at a point41 the track 40b associated with the lower roller 39a enters into thearcuate fishtail portion 40b of its track. As this is happening theupper roller 38a continues to ride vertically downward on its track 40a,thus causing the floor member 30 to tilt downward. As depicted at binlocation 20c in FIG. 1, the travel of the cam follower 390 about thearcuate path portion 40b of its track, while the other cam follower 38acontinues its vertical travel, progressively causes a downward tiltingof the support floor 30 in a vertical arc approaching 45 with thehorizontal at the end of the cam travel when the upper roller 38::reaches stop 43. Tightening up of the cables 42 causes the floor member30, moving on its cam followers, to return to the horizontal andthereafter progress vertically upward along the guide 40.

Referring to FIG. 4, which shows details of the cable and drivemechanism for the floor member 30, the pair of upper radial flanges 38attached to either end of the tubular shaft 34 are connected to a pairof respective support chain cables 42a, 42b. The cable 42b connecting tothe far end of the shaft passes over sprocket pulley 45 and thenceoverhead along the upper edge of the bin wall 22 to come adjacent to thecable 42a attached to the near shaft end. Both cables next pass over apair of respective sprocket pulleys 46, 47 and then downwardly over apair of respective sprocket rollers 48, 49 carried on a clevis 50attached to the rod 51 ofa hydraulic actuator 52. In lieu of a hydraulicactuator other suitable means such as a motor-driven winch can be usedfor reciprocably positioning the sprocket rollers 48, 49. The cablesthereafter pass upward to terminate at tie points 54, 55 fastened to thewall stanchion 28. A turnbuckle is preferably provided on chain cable42b so as to enable the lateral axis of the floor member 30 to beadjusted to a level position. The cylinder end of the actuator 52 issecured to a support member 57 in the wall stanchion and thereciprocating movement of its rod 51 is controlled by suitable flowlines (not shown) connected to the cylinder. The pulley and cablearrangement shown in FIG. 4 provide a 2-to-1 displacement advantage suchthat a given travel of the piston rod 51 results in a correspondingvertical displacement of twice that amount in the shaft member 34.

The clevis 50 attached to the distal end of the actuator rod carries aprojection 60 which is adapted to trip limit switches 64, 62 atrespective preselected upper and lower travel limits so as to generateappropriate positional signals for controlling the sorter operation.When the floor member reaches the uppermost point of travel,corresponding to an empty bin situation, a signal is generated by thetripping of switch 64. Similarly the lower limit of vertical travel, atthe point prior to dumping when the bin is nearly completely full ofboards (corresponding to the situation shown in bin location 2012 inFIG. 1), switch 62 is actuated to generate a second signal.

Referring again to FIG. 1, a photocell circuit 65, for sensing theinterruption of light beam 68, is provided to scan across the topsurface of each of the bin stalls 20. Appropriate electrical circuitryis provided such that temporary interruption of the light beam, such asoccasioned by the momentary passage of a dropped board therethrough (asis shown at bin location 20d) does not generate any signal from thephotocell circuit. However, upon the continuous interruption of thelight beam 68 for a predetermined minimum period of time, e.g., 2seconds, as occurs when the height of the lumber pile has reached thetop of the bin stall, then in that event a control signal is generatedby the photosensor. The operation of the bin sorter is such that, uponthe receipt of an actuating signal from the photosensor 65, indicatingthat the level of the boards in the pile forming in that particular binhas reached a predetermined height in the stall, an actuating signal issup plied to the hydraulic actuator 52. The operation of the actuator iscontrolled by suitable means known to the art such that the controlsignals generated by the photosensor 65 as the bin fills up causessuccessive incremental extensions of its piston rod, with consequentsuccessive incremental lowerings of the bin floor 30 over the range oftravel of the rod between the positional limit switches 62, 64. Thus,from an initially empty position (depicted at bin location a) with thesupport floor raised to the uppermost position, as boards are ejectedinto the bin and the pile builds up to the point where the light beam 68of the photosensor 65 is interrupted by the pile, a control signal isthen generated and supplied to the hydraulic actuator 52 to cause thefloor to lower to a new position beneath the previous floor location atwhich the pile height no longer interrupts the light beam. Eachsubsequent control signal generated by the photosensor will cause thebin floor to index successively downward, in increments, so as tomaintain the level of the lumber pile at all times near the top of thebin stall, thereby ensuring that all of the boards drop a minimumdistance (on the order of 2 feet or less) as they are ejected from theoverhead conveyor. This minimizes the possibility of damage or degradeof the boards in the sorting process and improves the compacted uniformbuildup of the pile. As an alternate to the optical sensor provided bythe light beamphotocell arrangement, other suitable sensor means, suchas one using sonic waves, might feasibly be employed to scan across thetop of the bin.

When the bin has become filled with lumber, as indicated by theactuation of the lower limit switch 62 subsequently followed by the pileheight causing the interruption of the light beam 68, or alternativelyby the generation of an appropriate signal provided by a counter sensingthe total number of boards supplied to an individual bin, then anappropriate visual signal such as an indicator light would be generatedto indicate to the operator this bin full condition. At this lowermostor predump position of the bin floor 30 (depicted at bin location 20b)the cam follower 39a associated with the lower radial flange 39 is nearthe end of its vertical travel and about to descend into the arcuateportion 40b of the track. In preferred embodiments of the invention thebin floor would remain at this pre-dump position, with appropriatecircuitry provided in the control portion of the bin sorter system toinhibit the ejection of further boards into the filled bin until it isemptied and ready for refilling.

Upon the receipt of an operator-generated bin dump signal supplied tothe actuator 52, the rod arm is further extended in one continuousmovement to the limit of its stroke. The consequent slackening of thecables causes the floor 30 to tilt downwardly in a vertical arc in themanner previously described. This tilting action (depicted at binlocation 20c) forms an opening in the bottom of the bin permitting thecontents to spill out onto the horizontal chain conveyor 80 travelingbeneath the bin stalls. The boards are quickly carried off by thisconveyor away from the bin stall and onward to a subsequent station.Thereafter, with the contents of the bin now emptied, the action of thehydraulic actuator 52 is reversed to cause the piston arm to retract,thereby tightening up the supporting cables 42 and causing the floormember to move upward (as depicted at bin location 206*), until it againreaches the topmost position (shown at bin location 20a) ready toreceive a new supply of boards in the next cycle of bin filling. Byvirtue of the unique bin floor drive mechanism and conveyor arrangementprovided in the sorter system disclosed herein, the dumping of the bincontents and the restoration of the bin ready for refilling is carriedout extremely quickly and may be effected automatically following theinitiation by the operator of the bin dump signal.

The terms and expressions which have been employed in the foregoingabstract and specification are used therein as terms of description andnot of limitation, and there is no intention, in the use of such termsand expressions, of excluding equivalents of the features shown anddescribed, or portions thereof, it being recognized that the scope ofthe invention is defined and limited only by the claims which follow.

What is claimed is:

l. A lumber bin sorter of the type having a multiplicity of bins towhich graded lumber is carried by an overhead conveyor and ejected intodesignated bin locations with at least some of the bins being providedwith a floor member vertically movable between a topmost position whenthe bin is empty and a lowermost position when the bin is filled up withlumber, and having means for providing an opening in the bottom of saidbin for dumping its contents, characterized in that sensor means areprovided for generating a pair of signals indicating respectively thatsaid floor member has descended to said lowermost position and that thelumber pile formed in said bin has reached a predetermined height, theoccurrence of said pairs of signals serving to indicate that said bin isfull and ready for dumping.

2. A lumber bin sorter apparatus comprising: an overhead conveyorcarrying individual pieces of graded lumber and ejecting pieces of likecharacter into a designated one of a multiplicity of bin storagelocations, each of said bin storage locations being formed by a pair oflaterally spaced front and rear wall members together with a floormember for catching and supporting lumber pieces dropping into said binlocation, said floor member being formed of a plurality of support armsprojecting out from and axially spaced along a common horizontal shaftpositioned proximate and parallel to one of said bin walls andvertically movable between a topmost position when the bin is empty anda lowermost position when the bin is full, said floor member furthercontaining shielding means secured to said shaft and extending to thenearer of said bin wall pair for guiding falling lumber toward thecenter of said bin and to prevent boards from jamming between said shaftand said near wall; and operable means for forming an opening in thebottom of said bin for permitting the contents thereof to dump out ofsaid bin.

3. A lumber bin sorter apparatus comprising: an overhead conveyorcarrying individual pieces of graded lumber and ejecting pieces of likecharacter into a designated one of a multiplicity of bin storagelocations, each of said bin storage locations being formed by a pair oflaterally spaced front and rear wall members together with a floormember for catching and supporting lumber pieces dropping into said binlocation, said floor member being vertically movable between a topmostposition when the bin is empty and a lowermost position when the bin isfilled, and formed of a plurality of support arms projecting out fromand axially spaced along a common horizontal shaft aligned parallel tosaid bin walls, with a respective flange member attached at either endof said shaft and containing cam follower means in the form of a pair ofrollers riding on respective surfaces of a guide track guiding the pathof travel of said floor member, said pair of guide track surfaces beingof generally straight parallel orientation over the major part of theirlength for guiding said floor member in a vertical path between saidtopmost position and said lowermost position, and over the remainingportion one of said guide track surfaces follows an arcuate path, whilethe other continues substantially vertically, thereby causing said floormember to tilt downward in a vertical arc so as to form an opening inthe bottom of said bin for permitting the contents thereof to dump outof said bin.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 653506 Dated A211 1 4 1 212 Inv n Donald B. Turner: Albert H. Barnes It iscertified that error'appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Abstract Change "pints" to --points--.

Signed and sealed this 25th day of July 1972.

' (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer CommissionerofPatents USCOMM-DC 6O376-P69 u.s. GOVERNMENT PRINTlNG OFFICE: 1959mass-334 7 FORM PO-1050(10-69)

1. A lumber bin sorter of the type having a multiplicity of bins towhich graded lumber is carried by an overhead conveyor and ejected intodesignated bin locations with at least some of the bins being providedwith a floor member vertically movable between a topmost position whenthe bin is empty and a lowermost position when the bin is filled up withlumber, and having means for providing an opening in the bottom of saidbin for dumping its contents, characterized in that sensor means areprovided for generating a pair of signals indicating respectively thatsaid floor member has descended to said lowermost position and that thelumber pile Formed in said bin has reached a predetermined height, theoccurrence of said pairs of signals serving to indicate that said bin isfull and ready for dumping.
 2. A lumber bin sorter apparatus comprising:an overhead conveyor carrying individual pieces of graded lumber andejecting pieces of like character into a designated one of amultiplicity of bin storage locations, each of said bin storagelocations being formed by a pair of laterally spaced front and rear wallmembers together with a floor member for catching and supporting lumberpieces dropping into said bin location, said floor member being formedof a plurality of support arms projecting out from and axially spacedalong a common horizontal shaft positioned proximate and parallel to oneof said bin walls and vertically movable between a topmost position whenthe bin is empty and a lowermost position when the bin is full, saidfloor member further containing shielding means secured to said shaftand extending to the nearer of said bin wall pair for guiding fallinglumber toward the center of said bin and to prevent boards from jammingbetween said shaft and said near wall; and operable means for forming anopening in the bottom of said bin for permitting the contents thereof todump out of said bin.
 3. A lumber bin sorter apparatus comprising: anoverhead conveyor carrying individual pieces of graded lumber andejecting pieces of like character into a designated one of amultiplicity of bin storage locations, each of said bin storagelocations being formed by a pair of laterally spaced front and rear wallmembers together with a floor member for catching and supporting lumberpieces dropping into said bin location, said floor member beingvertically movable between a topmost position when the bin is empty anda lowermost position when the bin is filled, and formed of a pluralityof support arms projecting out from and axially spaced along a commonhorizontal shaft aligned parallel to said bin walls, with a respectiveflange member attached at either end of said shaft and containing camfollower means in the form of a pair of rollers riding on respectivesurfaces of a guide track guiding the path of travel of said floormember, said pair of guide track surfaces being of generally straightparallel orientation over the major part of their length for guidingsaid floor member in a vertical path between said topmost position andsaid lowermost position, and over the remaining portion one of saidguide track surfaces follows an arcuate path, while the other continuessubstantially vertically, thereby causing said floor member to tiltdownward in a vertical arc so as to form an opening in the bottom ofsaid bin for permitting the contents thereof to dump out of said bin.